1. The no-load current of the motor is large
When the no-load current of the motor is greater than the limit data, it indicates that the motor has malfunctioned. The reason for the large no-load current of the motor is that the internal mechanical friction of the motor is large, the coil is partially short-circuited, and the magnetic steel is demagnetized. We continue to do related tests and inspection items, and we can further determine the cause of the failure or the location of the failure.
If the motor's no-load/load speed ratio is greater than 1.5, turn on the power and turn the handle to make the motor run at a high speed and no-load for more than 10 seconds. After the motor speed stabilizes, measure the maximum no-load speed N1 of the motor at this time. Under standard test conditions, drive a distance of more than 200m, and start measuring the maximum load speed N2 of the motor. No-load/load ratio=N2÷N1.
When the motor's no-load/load speed ratio is greater than 1.5, it indicates that the magnets of the motor have been demagnetized quite badly. The entire set of magnets in the motor should be replaced. In the actual repair process of electric vehicles, the entire motor is generally replaced.
2. Motor heats up
The direct cause of motor heating is due to the large current. The relationship between motor current I, motor input electromotive force E1, motor rotation induced electromotive force (also called back electromotive force) E2, and motor coil resistance R is: I=( E1-E2) ÷R, I increases, indicating that R decreases or E2 decreases. The decrease in R is generally caused by a short circuit or open circuit of the coil, and the decrease of E2 is generally caused by the demagnetization of the magnetic steel or a short circuit or open circuit of the coil. In the practice of whole-vehicle maintenance of electric vehicles, the method to deal with the problem of motor heating is generally to replace the motor.
3. There is mechanical collision or mechanical noise inside the motor during operation
Regardless of high-speed motor or low-speed motor, there should be no mechanical collision or discontinuous irregular mechanical noise when the load is running. Different types of motors can be repaired in different ways.
4. The vehicle mileage is shortened and the motor is weak
The reasons for the short mileage of the car and the lack of power of the motor (commonly known as the lack of power of the motor) are more complicated. But after we have eliminated the above 4 kinds of motor faults, generally speaking, the fault of the vehicle with a short continuous mileage is not caused by the motor. This is related to the attenuation of the battery capacity, the charger is not fully charged, and the controller parameter drift (PWM The signal does not reach 100%) and so on.
5. Phase loss of brushless motor
The lack of phase of the brushless motor is generally caused by the damage of the Hall element of the brushless motor. We can measure the resistance of the output lead of the Hall element relative to the Hall ground wire and the lead wire of the Hall power supply, and use the comparison method to determine which Hall element is faulty.
In order to ensure the precise commutation position of the motor, it is generally recommended to replace all three Hall elements at the same time. Before replacing the Hall element, it is necessary to find out whether the phase algebraic angle of the motor is 120° or 60°. Generally, the three hall elements of the 120° phase angle motor are placed in parallel. For a 60° phase angle motor, one hall element among the three hall elements is placed in a 180° flipped position.